Bonded abrasives formed by uniaxial hot pressing

ABSTRACT

A particular method includes uniaxially hot pressing a preform that includes abrasive particles in a bonding material to form a bonded abrasive body.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from U.S. Provisional PatentApplication No. 61/540,972 entitled “Bonded Abrasives Formed by UniaxialHot Pressing,” by Marc Linh Hoang filed Sep. 29, 2011, which isincorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to bonded abrasives, and moreparticularly to forming bonded abrasive articles through uniaxial hotpressing.

BACKGROUND

Uniaxial pressing has typically been restricted to bodies having uniformcross-sections, as non-uniform cross-sections may react unpredictably tothe application of pressure. Pressure applied to a body having anon-uniform cross-section may result in a distortion of shape and/ornon-uniform density. Uniaxial hot pressing has also typically beenrestricted to bodies having uniform compositions, in order to avoiddiffering amounts of shrinkage resulting from variable coefficients ofthermal expansion. Differing amounts of shrinkage can result in regionsof partially undensified material or regions of increased stress.

U.S. Pat. No. 4,153,666 discloses hot pressing a preformed shape whichdeforms orderly to a final shape in a mold against preformed partshaving surfaces exactly mating with the surfaces of the preform. Thepreformed parts are formed of a powdered composition having the samecompaction ratio as the preform and a coefficient of thermal expansionsubstantially equal to that of the preform.

U.S. Pat. Nos. 6,306,325 and 6,508,964 disclose hot pressing ceramicbodies in a mold, wherein the ceramic bodies are homogeneous incomposition.

U.S. Pat. No. 3,467,745 discloses hot pressing refractory carbide bodieswith shaped cavities by incorporating a water-reactive carbide inamounts and at locations corresponding to the locations and size of thecavities desired in the final body. The water-reactive carbide may beleached out with water following pressing.

U.S. Pat. No. 5,250,130 discloses hot pressing a green body with anon-uniform compositional cross-section relative to the axial directionby laminating auxiliary material with the green body in the axialdirection to achieve a uniform shrinkage that is substantially equalacross the laminate. The auxiliary material is delaminated from the bodyafter hot pressing.

SUMMARY

In a particular embodiment, a method includes uniaxially hot pressing apreform that includes abrasive particles in a bonding material to form abonded abrasive body.

In another embodiment, a method includes uniaxially hot pressing apreform that includes abrasive particles to form a body having a reliefextending from a plane on the body that is parallel to an axis ofpressing.

In another embodiment, a method of forming a bonded abrasive bodyincludes forming a green body comprising abrasive particles and abonding material. The method further includes placing the green body ina mold and uniaxially hot pressing the green body to form the bondedabrasive body.

In another embodiment, a method includes forming a mixture of abrasiveparticles and bonding material, forming the mixture into a green body,and placing the green body in a mold. The method further includesuniaxially hot pressing the mold to form a bonded abrasive body with anear net shape that is asymmetric around a pressing axis.

In another embodiment, a method includes uniaxially hot pressing a greenbody preform to form a composite body. Pressing includes liquid phasesintering, and during pressing the geometry of the preform issubstantially altered.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousobjects, features, and advantages made apparent to those skilled in theart by referencing the accompanying drawings.

FIG. 1 includes a flow diagram illustrating a particular embodiment of amethod of making an abrasive tool having a relief.

FIG. 2 a includes an illustration of a preform in accordance with anembodiment disclosed herein.

FIG. 2 b includes a top view illustration of the exemplary preform ofFIG. 2 a.

FIG. 3 a includes an illustration of a particular embodiment of a singlemold for making an abrasive tool.

FIG. 3 b includes an illustration of a particular embodiment of a moldfor use in a mold pack for making an abrasive tool.

FIG. 4 includes an illustration of a particular embodiment of a loadedmold before pressing.

FIG. 5 includes an illustration of a particular embodiment of a loadedmold pack before pressing.

FIG. 6 includes a cross-sectional view to illustrate a particularembodiment of a pressing operation.

FIG. 7 includes an illustration of a particular embodiment of a moldafter pressing.

FIG. 8 includes an illustration of a particular embodiment of a moldpack after pressing.

FIG. 9 a includes an illustration of a particular embodiment of anabrasive tool with a relief.

FIG. 9 b includes an illustration of a plane of the exemplary abrasivetool of FIG. 9 a.

FIG. 9 c includes a side-view illustration of the exemplary abrasivetool of FIGS. 9 a and 9 b.

FIGS. 10 a, 10 b, and 10 c include illustrations of multiple exemplaryembodiments of abrasive tools with alternative relief orientations.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

According to one aspect of the present disclosure, a method is disclosedthat includes uniaxially hot pressing a preform that includes abrasiveparticles in a bonding material to form a bonded abrasive body. Withuniaxial hot pressing, a force is applied to a body in substantially onedirection or along a single axis while heat is applied to the body suchthat the geometric shape of the body is substantially changed. The axisalong which force is applied during uniaxial hot pressing is referred toherein as the axis of pressing. Thus, according to one aspect of thepresent disclosure, a bonded abrasive body may be formed by hot pressinga preform (e.g., a green or unsintered body) along a single axis (i.e.,the axis of pressing).

FIG. 1 includes a method 100 of making an abrasive tool using a uniaxialhot pressing process according to an embodiment. The method 100 includescombining abrasive particles with a bonding material to form a mixture,at step 102. The abrasive particles can include inorganic materials,such as oxides, carbides, nitrides, borides, oxynitrides, oxycarbides,or a combination thereof. In one particular instance, abrasive particlescan include alumina, silica carbide, silica, ceria, or a combinationthereof. Particular embodiments may utilize abrasive particles made ofsuperabrasive material. Suitable superabrasives may include diamond,cubic boron nitride (CBN), or a combination thereof. In one particularembodiment, the abrasive particles can consist essentially of diamond.Further, in another particular embodiment, the abrasive particles caninclude diamond grit present in an amount of 3.5% vol % or less.

The bonding material can include an inorganic material. In anembodiment, the major content (e.g., greater than 50% by volume, weight,or molar percentage) of the bonding material may include an inorganicmaterial. For example, the bonding material may be a ceramic, such as avitreous material.

In another example, the bonding material may include a metal or a metalalloy. For example, the bonding material can include one or moretransition metal elements. Suitable transition metal elements caninclude, but are not limited to, vanadium, chromium, manganese, iron,cobalt, nickel, copper, zinc, tin, zirconium, silver, molybdenum,tantalum, tungsten, or a combination thereof. Specifically, the bondingmaterial can include one or more transition metal elements selected fromthe group including cobalt, iron, copper, and nickel. In a particularaspect, the bonding material can include an electrolytic iron powder,pre-alloyed bronze, a nickel base alloy, or a combination thereof. In anexemplary, non-limiting embodiment, the bonding material can include 40wt % electrolytic iron powder (−315 mesh), 48 wt % water atomizedpre-alloyed bronze 90/10 (−200 mesh), and 12 wt % nickel base alloy(53-75 μm).

In another example, the bonding material can include an organicmaterial. In an embodiment, the major content (e.g., greater than about50% by volume, weight, or molar percentage) of the bonding material mayinclude an organic material. Illustrative organic materials can includepolymers such as glycol, resin, dextrin, glue, polyethylene, ethylene,propylene, polyvinyl alcohol, or a combination thereof. In a particularinstance, the bonding material may be a resin. Illustrative resins mayinclude thermosets, thermoplastics, or a combination thereof. Forexample, resins can include phenolics, such as novolak and resole,epoxies, polyesters, such as unsaturated polyesters, cyanate esters,shellacs, polyurethanes, rubber, polyimides, bismaleimides, melamines,or a combination thereof.

Other embodiments may use a bonding material made of a compositematerial, including for example, a combination of organic and inorganicmaterials. For example, the bonding material can include a combinationof a metal material combined with a polymer material (e.g., a resin).

In addition to the abrasive particles and bonding materials, the mixturemay contain other materials, such as additives. It will be appreciatedthat additives may be included within the mixture to facilitate properformation of the final abrasive body. Examples of such additives caninclude stabilizers, binders, surfactants, pore formers, and the like.The additives can also include lubricants, such as a graphite powderlubricant additive (50-150 mesh). In a particular aspect, such lubricantadditives can be present in an amount less than or equal to 5.0 vol %.

Following formation of the mixture including abrasive particles and abinding material, the mixture can be formed into a preform, at step 104.For example, FIGS. 2 a and 2 b depict an exemplary embodiment of apreform 200. After formation of the preform, the preform may be placedin a mold, at 106. The mold may include an opening, shaped to hold apreform, and one or more recesses positioned adjacent to the opening. Asan illustrative example, FIG. 3 a depicts an embodiment of a mold 300 tohold a single preform (e.g., the preform 200 of FIG. 2), and FIG. 4depicts an exemplary embodiment of a loaded mold before pressing (e.g.,the mold 300 of FIG. 3 a loaded with the preform 200 of FIG. 2).

After the preform has been placed in the mold, the process can continue,at step 108, by uniaxially hot pressing the preform within the mold(e.g., the loaded mold of FIG. 4) to form a finally-formed abrasivebody. In particular processes according to embodiments herein, duringuniaxial hot pressing, the geometry of the preform can be substantiallyaltered, such that the geometry of the preform is measurably altered andforms a finally-formed abrasive body having a geometry significantlydifferent than the shape of the preform. In one embodiment, the geometryof the preform can be altered during uniaxial hot pressing to form afinally-formed abrasive body having a relief. As described in accordancewith embodiments herein, the shape of the relief may depend on the shapeof the mold used to hold the preform.

As described herein, FIG. 1 illustrates a particular embodiment of amethod of forming a bonded abrasive body having a relief by hot pressinga preform (e.g., a green or unsintered body) along a single axis (i.e.,the axis of pressing). The abrasive particles and the bonding materialof a particular preform may be selected based on the type of abrasivetool to be formed.

FIGS. 2 a and 2 b depict an exemplary embodiment of a preform 200. Asillustrated in FIGS. 2 a and 2 b, the preform 200 can have a bodydefined by a top surface 202 and a bottom surface 204 opposite the topsurface 202. As illustrated, in particular instances, the top surface202 and the bottom surface 204 may have curved contours, andparticularly, may define convex and concave surfaces, respectively. Thebody of the preform 200 can also be defined by a front surface 225 and arear surface 226, which are substantially planar surfaces that aresubstantially parallel to each other. The body of the preform 200 canalso include a side surface 227 extending at an angle to the frontsurface 225 and the rear surface 226, which may be a substantiallyorthogonal angle, and join the front surface 225 and the rear surface226. The body of the preform 200 can also include a side surface 228,spaced apart from the side surface 227 by a width (W) of the bodydefined along a horizontal axis 208. The side surface 228 can extend atan angle to the front surface 225 and the rear surface 226, which may bea substantially orthogonal angle, and join the front surface 225 and therear surface 226.

In another aspect, one or more of the preform surfaces 202, 204 may notbe contoured, but may be flat and extend along and define a singleplate. These surfaces 202, 204 may become contoured during the formingprocess and may remain contoured after the forming process.

As further illustrated in FIG. 2 a, the body of the preform 200 can havea length (L) defined as the longest dimension along a longitudinal axis206, a width (W) defined as a dimension orthogonal to the length (L)along the horizontal axis 208, and a thickness (T) defined as thedimension along the side surfaces 227 and 228 perpendicular to a planedefined by the front surface 225 and the rear surface 226. The preform200 may have a cross-sectional shape which is symmetrical about thelongitudinal axis 206, as viewed in a plane defined by the length (L)and the thickness (T). Additionally, as illustrated in FIG. 2 b, thepreform 200 can have a cross-sectional shape that is symmetrical about ahorizontal axis 208 as viewed in a plane defined by the width (W) andthe thickness (T). In the particular embodiment illustrated in FIGS. 2 aand 2 b, the thickness (t) of the preform 200 can be uniform.

In one embodiment, the preform 200 may be a green body. It will beappreciated that a green body can be an unfinished article, for example,an unsintered material. It will be further appreciated that a green bodycan be a body which is not fully densified, which may undergo furtherprocessing to affect grain growth and densification. The preform 200 maybe formed by a variety of forming methods, including pressing, such ashot pressing or cold pressing, molding, casting, extruding, or acombination thereof. According to one particular process, the green bodycan be formed by cold pressing.

In particular instances, the forming process can include the formationof a green body that has a general shape which lacks at least one designfeature of the finally-formed abrasive body formed through uniaxial hotpressing. Exemplary design features can include protrusions, recesses,patterned features, and the like.

The preform 200 can include a particular content of porosity within thegreen body, a particular content of abrasive particles within the greenbody, and a particular content of bonding material within the greenbody. Further, the content of porosity within the green body, thecontent of abrasive particles within the green body, and the content ofbonding material within the green body can depend on a variety offactors. These factors can include, but are not limited to, the size ofthe preform 200, the percentage of compaction to be applied on thepreform 200 during processing (i.e., the intended amount of volumeshrinkage), the compactability of the bonding material within the greenbody, the compactability of the abrasive particles, and thecompactability of any fillers or additives, etc.

Depending upon certain processing parameters, the properties of thepreform 200 can change during the forming process. For example, the sizeof at least a portion of the pores can be reduced during the formingprocess. Moreover, at least a portion of the pores can be collapsed andeliminated during the forming process. As such, the porosity of thepreform 200 can be reduced during the forming process, and the porosityof the abrasive tool formed from the preform can be less than theporosity of the preform 200 before the forming process. Theconcentration of abrasive particles can also change due to a change inthe volume of the preform 200 during the forming process to form theabrasive tool. For example, as the volume of the preform 200 is reducedduring formation, the concentration of abrasive particles can increasewhen expressed as a percentage of total volume. The forming process canbe controlled to precise condition, such that the final content of thephases (e.g., bond material, abrasive particles, fillers, and evenporosity) can be precisely controlled.

FIG. 3 a depicts an exemplary embodiment of a mold 300 that is shaped tohold a single preform (e.g., the preform 200 of FIG. 2). According to anembodiment, the mold 300 may include carbon, and may be made of carbon,such that the mold 300 can be a carbon-based composition. It will beappreciated that “carbon-based” refers to compositions including atleast 50% carbon. In another example, the mold 300 can be substantiallycarbon. Further, such mold consists essentially of carbon. For example,the mold 300 can be graphite.

In the embodiment illustrated in FIG. 3 a, the mold 300 can include anupper portion 308 and a lower portion 309 separate from the upperportion 308 and defining an opening 302 there between. The opening 302can be shaped to receive the preform 200. In particular, the upperportion 308 can have a surface 318 defining an upper boundary of theopening 302 and configured to directly contact a surface (e.g., lowersurface 204) of the preform 200 during pressing. In particular, thesurface 318 of the upper portion 306 can have a complementary curvatureto the curvature of the lower surface 204 of the preform 200 for fullcontact during pressing. The lower portion 309 can have a surface 319defining a lower boundary of the opening 302 and configured to directlycontact a surface (e.g., upper surface 202) of the preform 200 duringpressing. In particular, the surface 319 of the lower portion can have acomplementary curvature to the curvature of the upper surface 202 of thepreform 200 for full contact during pressing.

As further illustrated, the mold 300 can include a rear portion 310. Therear portion can be configured to engage a portion of the preform 200during pressing, and in particular, may engage the preform 200 along aportion of the rear surface 226 during pressing. According to oneembodiment, the rear portion 310 of the mold 300 can include a recess304. The recess 304 can be an opening extending into the volume of therear portion 310. The recess 304 can be positioned adjacent to theopening 302 and be in fluid communication with the opening 302. Therecess 304 may have a shape that corresponds to a design feature of thefinally-formed abrasive body (e.g., a relief or a relief pattern). Inone exemplary embodiment, the recess 304 can include a surface 314defining a bottom surface of the recess 304 that is spaced apart fromthe front surface 312 of the rear portion 310. The surface 314 may havea particular contour, such as a smooth contour, or alternatively, arough surface defined by patterned features or protrusions.

In particular instances, the recess 304 can extend along the full widthof the rear portion 310 between side surfaces 333 and 334, such that therecess 304 intersects with the side surfaces 333 and 334. However, inother embodiments, the recess 304 may extend for a fraction of the fullwidth of the rear portion 310.

According to one particular embodiment, the recess 304 can have aparticular contour. For example, the contour of the recess 304 can besimilar to the contour of the surfaces 318 or 319 of the mold 300. Inparticular, the recess 304 may have a curvilinear contour, defining aconvex or concave arc.

FIG. 3 b includes an illustration of an alternative embodiment. Inparticular, FIG. 3 b illustrates a mold portion, and more particularly,an alternative design for a rear portion 310. The rear portion 310 ofFIG. 3 b can be made of an upper portion 328 and a lower portion 329,wherein an opening is defined between the upper portion 328 and thelower portion 329. The upper portion 329 can have a recess 324, whichcan have the same characteristics of the recess 304 described inembodiments herein. The opening 322 can be shaped to receive a preform(e.g., preform 200). According to one embodiment, the upper portion 328and the lower portion 329 can have the same attributes as the upper andlower portions 308 and 309 as described in accordance with embodimentsherein. Partitioning of the rear portion 310 into upper and lowerportions 328 and 329 can facilitate processing of multiple preforms in amold pack, which will be described in more detail herein.

FIG. 4 includes an illustration of a loaded mold according to anembodiment. In particular, the mold has been loaded with a preform 200between the upper portion 308 and lower portion 309. As illustrated inFIG. 4, the lower surface 204 of the preform 200 can be in directcontact with the surface 318 of the upper portion 308 of the mold 300,and the lower surface 202 of the preform 200 can be in direct contactwith the surface 319 of the lower portion 309 of the mold 300. Moreparticularly, the lower surface 204 of the preform 200 can directlycontact the surface 318 of the upper portion 308 along the full width ofthe preform 200. Additionally, the surface 202 of the preform 200 candirectly contact the surface 319 of the lower portion 309 along the fullwidth of the preform 200. It will be appreciated that directlycontacting the mold 300 refers to instances where there are nointervening layers between the preform 200 and the mold portions 308 and309.

Furthermore, the rear surface 226 of the preform 200 can be in directcontact with a surface 312 of the rear portion 310 of the mold 300.Notably, however, a portion of the rear surface 226 can be spaced apartfrom the rear portion 310 at the recess 304, wherein the recess 304includes a surface 314 defining the bottom of the recess 304, and thesurface 314 can be spaced apart from the rear surface 226 of the preform200. The space between the surface 314 and the rear surface 226 may befilled with material of the preform 200 during the pressing process.

FIG. 5 includes an illustration of a mold pack according to anembodiment. The mold pack 500 facilitates processing and shaping ofmultiple preforms 531 and 532 in a single uniaxial pressing operation.For example, the mold pack 500 can include a first mold portion 510having an upper portion 511 and a lower portion 512 corresponding to theupper and lower portions 308 and 309 of the mold 300. A first preform531 can be positioned between the upper and lower portions 511 and 512.However, the lower portion 512 can include a recess 513 formed in itsrear surface 515, wherein the recess 513 extends into the volume of thelower portion 512. The recess 513 can have any features of recessesdescribed in embodiments herein.

The mold pack 500 can include a second mold portion 520 including anupper portion 521 and a lower portion 522. The upper and lower portions521 and 522 can have the features of mold portions described in theembodiments herein. In particular, the upper portion 521 can have arecess 523 formed in its front surface 525, wherein the recess 523extends into the volume of the upper portion 521.

In particular, the mold pack 500 can utilize the first and second moldportions 510 and 520, which are oriented with respect to each other tofacilitate processing of multiple preforms in a single pressingoperation. Notably, during pressing, the first and second mold portions510 and 520 can be uniaxially pressed and compressed uniformly at thesame rate, such that the preforms 531 and 532 are processedsimultaneously. In particular, the recesses 513 and 523 can be orientedwith respect to the preforms 531 and 532 in the opposing mold portions510 and 520 to facilitate suitable formation of features (e.g., reliefs)in the preforms 531 and 532 during pressing

While the exemplary mold pack 500 illustrated in FIG. 5 includes twomold portions 510 and 520, alternative embodiments can include more thantwo mold portions. For example, a mold pack may include at least threemolds. In another example, a mold pack may include at least four molds.

FIG. 6 is a cross-sectional illustration of a uniaxially hot pressingprocess according to an embodiment. In particular, the uniaxial hotpressing construction includes a mold construction 600 loaded with apreform 602, which can include any preforms described in embodimentsherein. According to one embodiment, the mold construction 600 caninclude a mold 630 having an upper portion 608 and a lower portion 609having the features of upper and lower portions described in embodimentsherein. The mold construction 600 can also include die portions 660 and661 configured to contain a least a portion of the preform 602 withinthe mold construction 600, and may directly contact a portion of thepreform 602 along its sides during a pressing operation. The moldconstruction 600 may further include an upper punch 662 that can bepositioned above the upper portion 608, and in particular, can directlycontact the upper portion 608 during a pressing operation. The moldconstruction 600 can further include a lower punch 663 that can bepositioned below the lower portion 609, and in particular, can be indirect contact with the lower portion 609 during a pressing operation.

During a uniaxial pressing operation, a force (illustrated as “F” inFIG. 6) may be applied to the preform 602 along an axis of pressing(illustrated as “A” in FIG. 6). In particular, during a pressingoperation, a force F can be applied along the single pressing axis A onthe upper punch 662 to compact the preform 602 between the upper andlower portions 608 and 609. It will be appreciated that a force appliedto a body may be translated into a pressure, depending upon thecross-sectional dimensions of the preform 602. Alternatively, twoopposing forces can be applied from the top and bottom of the moldconstruction 600, such as equal and opposing forces on the upper punch662 and the lower punch 663 to compact the preform 602 between the upperand lower portions 608 and 609. For illustrative purposes only, onepreform 602 is illustrated as loaded into the mold 630. However, it willbe appreciated that the mold 630 can be formulated to contain more thanone preform, as described in embodiments herein. In this case, aplurality of abrasive bodies may be produced from multiple preforms in asingle pressing operation.

The forming process can include particular forming parameters. Forexample, the pressure applied may be dependent in part upon variousfactors, including but not limited to, particular components within thepreform, content of phases within the preform, amount of shrinkageintended between the preform and the finally-formed bonded abrasivearticle, the temperature applied, the atmosphere, and the like.

According to one embodiment, a preform 602 that includes bondingmaterial comprising metal can be uniaxially hot pressed at a pressure ofat least about 4.9 MPa (710 psi). In other embodiments, the forceapplied during the uniaxial hot pressing operation can be a pressure onthe preform 602 of at least about 9.8 Mpa (1421 psi), such as at leastabout 14.7 MPa (2132 psi), or even at least about 19.6 MPa (2842 psi).Still, according to one embodiment, the pressure may be not greater thanabout 44.1 MPa (6398 psi), such as not greater than about 39.2 MPa (5685psi), not greater than about 34.3 MPa (4975 psi), or even not greaterthan about 29.4 MPa (4264 psi). It will be appreciated that the preform602 that includes a binding material comprising metal may be uniaxiallyhot pressed at a pressure within a range including any of the minimumand maximum values noted above.

Uniaxial hot pressing may be conducted in a particular atmosphere. Forexample, in one process according to an embodiment, the preform 602 canbe uniaxially hot pressed in an atmosphere comprising air. In anotherexample, the preform 602 can be uniaxially hot pressed in an inertatmosphere. It will be appreciated that an “inert atmosphere” refers toan atmosphere that does not include gases that may react with thecomponents of the preform 602 during pressing. In another example, thepreform 602 can be uniaxially hot pressed in an oxidizing atmosphere.Alternatively, the preform 602 may be uniaxially hot pressed in areducing atmosphere.

According to one embodiment, uniaxial hot pressing can includeapplication of heat simultaneously with the application of a uniaxialforce. The forming process can include particular forming temperature,which may be dependent in part upon various factors, including but notlimited to, particular components within the preform, content of phaseswithin the preform, amount of shrinkage intended between the preform andthe finally-formed bonded abrasive article, the temperature applied, theatmosphere, and the like.

For example, for a preform 602 including a bonding material comprisingmetal, the uniaxial hot pressing can be conducted at a temperature of atleast about 600° C. (1112° F.), such as at least about 650° C. (1202°F.), at least about 700° C. (1292° F.), or even at least about 750° C.(1382° F.). In a particular embodiment, the temperature may be notgreater than about 1100° C. (2012° F.), such as not greater than about1000° C. (1832° F.), not greater than about 900° C. (1652° F.), or evennot greater than about 800° C. (1472° F.). It will be appreciated thatuniaxially hot pressing may be conducted at a temperature within a rangeincluding any of the minimum and maximum temperatures noted above.

During the pressing operation, the preform 602 may be heated to atemperature such that the preform 602 is formed through a liquid phasesintering process. It will be appreciated that liquid phase sintering isa method of sintering, wherein at least a portion of one phase of thepreform 602 (e.g., a portion of the bonding material) melts or becomesliquid. Notably, liquid phase sintering can also include thedensification of the preform 602 into a finally-formed abrasive article.In one embodiment, liquid phase sintering can include changing at leasta portion of the bonding material composition of the preform 602 into aliquid phase, wherein the liquid can change location within the mold 630and facilitate changing the geometry of the preform 602 during thepressing operation. In particular instances, the combination of thecomposition of the preform 602 and the pressing operation can facilitatemovement of the liquid phase through the preform 602 via capillaryaction to rearrange the unmelted particles into a more favorable packingarrangement.

Notably, during uniaxial hot pressing, a portion of the bonding materialof the preform 602 may soften or melt, allowing a portion of the bondingmaterial and abrasive particles to flow into one or more recesses of themold 630, resulting in a substantial change in the geometry of thepreform 602. The liquid phase of the bonding material may carry unmeltedportions of the bonding material and unmelted abrasive grains into therecess. For example, the geometry of at least one surface of the preform602 may be substantially altered during uniaxial hot pressing to includea relief projecting from a surface. According to a particularembodiment, at least a portion of the preform 602 can undergo liquidphase sintering and the liquid portion can flow into a recess (e.g.,recess 304 of FIG. 3 a) that is in fluid communication with an openingformed between upper and lower portions, wherein the preform 602 isdisposed within the opening.

In this manner, a net-shaped or near net-shaped abrasive body may beformed during the uniaxial hot pressing operation. It will beappreciated that a “net-shaped” abrasive body is one that has a geometrythat is essentially the same as the intended shape provided by the mold630 when the pressing operation is completed. A “net-shaped” abrasivebody may not necessarily require further shape-altering processing. A“near net-shaped” abrasive body is one that has a geometry that isessentially the same as the intended shape provided by the mold 630 whenthe pressing operation is completed and may require final processing,albeit minimal final processing.

FIG. 7 includes an exemplary embodiment of a mold 700 after uniaxial hotpressing is completed and a finally-formed abrasive body is formedaccording to an embodiment. In particular, the mold 700 includes anarrangement of an upper portion 708, a lower portion 709, a rear portion710, and a finally-formed abrasive body 702 contained within the mold700. As illustrated in FIG. 7, and according to one embodiment, afterconducting the uniaxial hot pressing operation, the geometric dimensionsof the preform have changed, such that the finally-formed abrasivearticle can include a relief 706, which is disposed into a recess 704 ofthe rear portion 710, and in particular, the relief 706 can have acomplementary shape to the shape of the recess 704. Accordingly, therelief 706 can have a three-dimensional shape corresponding to the shapeof the recess 704.

FIG. 8 depicts an exemplary embodiment of a loaded mold pack 800 afterconducting a uniaxial hot pressing operation. As will be appreciated,the loaded mold pack 800 can include multiple molds 810 and 820 suitablefor forming multiple preforms into finally-formed abrasive articles 831and 832 in a single uniaxial hot pressing operation. As described inembodiments herein, the uniaxial hot pressing operation can be conductedin a manner to facilitate a change in geometric shape to the preforms,such that at least one geometric dimension of the finally-formedabrasive articles 831 and 832 is different than a geometric dimension ofthe corresponding preforms. In particular, as illustrated in FIG. 8, thefinally-formed abrasive article 831 can have a relief 806 formed withinand having a shape complementary to the recess 812. The finally-formedabrasive article 832 can have a relief 807 formed within and having ashape complementary to the recess 813.

FIG. 9 a includes an illustration of an abrasive article according to anembodiment. In particular, the abrasive article can include an abrasivebody 900 defined by a top surface 902 and a bottom surface 904 oppositethe top surface 902, which are separated by a length (L) of the abrasivebody 900. In particular instances, the top surface 902 and the bottomsurface 904 may have curved contours, and particularly, may defineconvex and concave surfaces, respectively. The abrasive body 900 canalso include a side surface 927 extending at an angle to a front surface925 and a rear surface 926, which may be a substantially orthogonalangle, and join the front surface 925 and the rear surface 926. Theabrasive body 900 can also include a side surface 928, spaced apart fromthe side surface 927 by the width (W) of the body 900. The side surface928 can extend at an angle to the front surface 925 and the rear surface926, which may be a substantially orthogonal angle, and join the frontsurface 925 and the rear surface 926.

The abrasive body 900 can also be defined by a front surface 925 and arear surface 926, separated from each other by a thickness (T). Notably,the abrasive body 900 can include a relief 990 in the form of aprojection extending from the front surface 925. In particularinstances, the relief 990 can be defined by a first surface 991extending at an angle from the front surface 925 and a second surface992 extending at an angle from the front surface 925 and spaced apartfrom the first surface 991 by a third surface 993. As illustrated, afirst angle 995 can be defined between the first surface 991 and thethird surface 993. The first angle 995 can be an acute angle, an obtuseangle, or a substantially orthogonal angle. According to the illustratedembodiment of FIG. 9 a, the first angle 995 defines a substantiallyorthogonal angle.

As also illustrated, a second angle 996 can be defined between thesecond surface 992 and the third surface 993. The second angle 996 canbe an acute angle, an obtuse angle, or a substantially orthogonal angle.According to the illustrated embodiment of FIG. 9 a, the second angle996 defines a substantially orthogonal angle.

As will be further appreciated, while the relief 990 is illustrated ashaving a particular cross-sectional polygonal shape, such that anglesare defined between certain surfaces, other surfaces can be used todefine other particular polygonal shapes. For example, the relief 900can have a cross-sectional shape that is triangular, quadrilateral,pentagonal, hexagonal, or any other polygonal shape. Further, aquadrilateral relief can be a parallelogram, such as a rhombus, arhomboid, a rectangle, or a square. Moreover, the quadrilateral reliefcan be a trapezoid, a trapezium, or an isosceles trapezoid. In anotheraspect, the relief 990 can be defined by one or more curvilinearsurfaces, such that radiuses or rounded edges are utilized and therelief 990 can have a cross-sectional shape that is semicircular.Further, the relief can be formed into patterns that can includewording, letters, numbers, symbols, alphanumeric symbols, etc. In aparticular aspect, the patterns formed by the relief can be used toidentify the part in which the relief is formed.

According to an embodiment, the relief 990 can extend for at least aportion of the width (W) of the abrasive body 900 between the sidesurfaces 927 and 928. In another embodiment, the relief 990 can extendfor a full dimension of the width (W) of the body 900, such that therelief 990 intersects the side surfaces 927 and 928. Furthermore, asillustrated, the relief 990 can be formed such that the surfaces 991,992, and 993 have a curvature extending along the width (W) of theabrasive body 900. In particular, the surfaces 991, 992, and 993defining the relief 990 can have a same curvature extending along thedimension of the width (W), and define a same arc as the curvatures ofthe top and bottom surfaces 902 and 904 of the abrasive body 900.

FIG. 9 b includes a perspective view of the abrasive body 900. Asillustrated, the abrasive body 900 can have an asymmetry in a plane 950defined by the dimensions of the length (L) and the thickness (T) of theabrasive body 900. Notably, the relief 990 can extend at an angle fromthe front surface 925 and define an asymmetry to a plane that isparallel with an axis of pressing. In more detail, FIG. 9 c includes across-sectional view of the abrasive body 900 along the plane 950. Asillustrated, the body 900 can include a relief 990 extending from thefront surface 925, which is an exterior surface of the body 900, anddefine a plane 951 parallel to the axis (A) of force applied during theuniaxial hot pressing operation.

In a one embodiment, the relief 990 may include a design on the surfaceof the abrasive body 900. For example, the relief 990 may includeindicia, including for example, a logo, such as a company logo, aproduct logo, product number, or serial number. In particular instances,the relief 990 may be the indicia, including for example, a logo, suchas a company logo, a product logo, product number, or serial number.

FIGS. 10 a, 10 b, and 10 c include illustrations of abrasive articlesaccording to embodiments herein. In particular, the abrasive articlesinclude abrasive bodies demonstrating alternative designs according toembodiments. For example, FIG. 10 a includes an illustration of anabrasive article including a body 1000 having a relief 1090 extendingfrom the body 1000 at a right angle “R” to the axis of pressing A. Thatis, the relief 1090 of FIG. 10 a can define a right angle R between afirst surface 1091 and a front surface 1025.

As another example, FIG. 10 b includes an illustration of an abrasivearticle including a body 1051 having a relief 1090 extending from thebody 1051 at an acute angle “C” relative to the axis of pressing A. Thatis, the relief 1090 of FIG. 10 b can define an acute angle C between thefirst surface 1091 and the front surface 1025 of the body 1051.Accordingly, as illustrated, the relief 1090 may extend upward toward atop surface 1002 of the body 1051.

In a further example, FIG. 10 c includes an illustration of an abrasivearticle including a body 1052 having a relief 1090 extending from thebody 1052 at an obtuse angle “O” relative to the axis of pressing A.That is, the relief 1090 of FIG. 10 c can define an obtuse angle Cbetween the first surface 1091 of the relief 1090 and the front surface1025 of the body 1052. Accordingly, as illustrated, the relief 1090 mayextend downward toward a bottom surface 1004 of the body 1052.

In a particular embodiment, prior to the forming process, the preformmay include a particular content of porosity. For example, the preformcan include at least about 20 vol % porosity, such as at least about 25vol % porosity, at least about 30 vol % porosity, or even at least about35 vol % porosity for the total volume of the preform. Still, thepreform may include not greater than about 60 vol % porosity, such asnot greater than about 55 vol % porosity, not greater than about 50 vol% porosity, or not greater than about 45 vol % porosity for the totalvolume of the preform. It will be appreciated that the preform mayinclude a porosity content within a range including any of the minimumand maximum values provided above

According to another particular embodiment, upon completion of theforming process on the preform, the resulting abrasive body may include0 vol % porosity. In another embodiment, the body may include aparticular content of porosity. For example, the body may include atleast about 1 vol % porosity, such as at least about 3 vol % porosity,at least about 5 vol % porosity, or even at least about 10 vol %porosity for the total volume of the body. Still, the body may includenot greater than about 20 vol % porosity, such as not greater than about15 vol % porosity for the total volume of the body. It will beappreciated that the body may include a porosity content within a rangeincluding any of the minimum and maximum values provided above.

According to another embodiment, upon completion of the forming process,the abrasive body may include a particular content of bonding material.For example, the body may include at least about 10 vol % bondingmaterial for the total volume of the body. In certain other instances,the body can include at least about 15 vol % bonding material, at leastabout 20 vol % bonding material, or even at least about 25 vol % bondingmaterial. Still, the body may include not greater than about 70 vol %bonding material, such as not greater than about 65 vol % bondingmaterial for the total volume of the body. It will be appreciated thatthe body may include an amount of bonding material within a rangeincluding any of the minimum and maximum values provided above.

Example

In a particular embodiment, for uniaxial hot pressing along a length, L,of a preform, the length, L, is selected by considering, for example,the compactability of the mixture that comprises the preform and theexpected life of the compaction tools used to form the preform. Thefinal length of the preform should be selected such that wear on thecompaction tools due to the abrasive particles in the preform mixture islimited while providing sufficient compaction so the preform issufficiently strong enough to be handled readily without breaking whenplaced in a mold. For a bonding material comprising 30-100 wt % bronzeand 40-60 wt % iron and a final abrasive content of 2-12.5 vol % (asmeasured in the final abrasive body), the compaction pressure can bewithin a range that is between and includes about 68.9 Mpa (10.0 ksi) toabout 441.3 MPa (64.0 ksi), the hot pressing temperature can be withinand include a range of about 600° C. (1112° F.) to about 1100° C. (2012°F.), and the hot pressing pressure can be within and include a range ofabout 4.9 MPa (710 psi) to about 44.1 MPa (6398 psi).

In one instance, an abrasive body includes a preform mixture thatincludes:

-   -   a. a bonding material having 40 wt % electrolytic iron powder        (−315 mesh), 48 wt % water atomized pre-alloyed bronze 90/10        (−200 mesh), and 12 wt % nickel base alloy (53-75 μm);    -   b. 3.5 vol % of diamond grit abrasive particles; and    -   c. 5.0 vol % of graphite powder lubricant additive (50-150        mesh).

The preform mixture is compacted at a compaction pressure of about 372MPa (54 ksi) to form a preform that includes a length that is about 1.8times greater than the final abrasive body. The preform is hot pressedat a temperature of about 900° C. (1652° F.) and a pressure of about19.6 MPa (2842 psi) to form the abrasive body.

The embodiments herein represent a departure from the state-of-the-art.Traditionally, bonded abrasive articles are formed through processessuch as cold pressing or hot pressing. In such processes, forces areapplied evenly across the surface of the preform to form thefinally-formed abrasive body. Moreover, with respect to uniaxialpressing operations, such a process is reserved in the industry forthose materials having uniform compositions. Materials havingheterogeneous compositions are regarded as having differentialcompaction dynamics that can result in density gradients within thefinally-formed body and thus a poorly formed and unfit article. However,the present embodiments are directed to uniaxial hot pressing ofheterogeneous bodies including abrasive particles and bonding materialto form bonded abrasive articles. The embodiments herein utilize acombination of features, which include, but are not limited to,compositions of the preform, shape of the preform, composition and shapeof the molds, processing parameters including pressure, temperature, andatmosphere, liquid phase sintering, and changes in geometry between thepreform and finally-formed abrasive article, which facilitate theforming process and attributes of the finally-formed bonded abrasivebodies.

In the foregoing, reference to specific embodiments and the connectionsof certain components is illustrative. It will be appreciated thatreference to components as being coupled or connected is intended todisclose either direct connection between said components or indirectconnection through one or more intervening components as will beappreciated to carry out the methods as discussed herein. As such, theabove-disclosed subject matter is to be considered illustrative, and notrestrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true scope of the present invention. Thus, to the maximum extentallowed by law, the scope of the present invention is to be determinedby the broadest permissible interpretation of the following claims andtheir equivalents, and shall not be restricted or limited by theforegoing detailed description.

The Abstract of the Disclosure is submitted with the understanding thatit will not be used to interpret or limit the scope or meaning of theclaims. In addition, in the foregoing Detailed Description, variousfeatures may be grouped together or described in a single embodiment forthe purpose of streamlining the disclosure. This disclosure is not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter may bedirected to less than all features of any of the disclosed embodiments.Thus, the following claims are incorporated into the DetailedDescription, with each claim standing on its own as defining separatelyclaimed subject matter.

1. A method of forming a bonded abrasive body comprising: uniaxially hotpressing a preform comprising abrasive particles in a bonding materialto form a bonded abrasive body.
 2. The method of claim 1, wherein duringuniaxially hot pressing, the geometry of the preform is substantiallyaltered.
 3. The method of claim 1, wherein uniaxially hot pressingcomprises liquid phase sintering.
 4. (canceled)
 5. (canceled)
 6. Themethod of claim 1, further comprising uniaxially hot pressing in one ofan oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere.7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled)
 11. (canceled)12. (canceled)
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 33. The method of claim 1,further comprising forming a green body preform comprising abrasiveparticles and a bonding material.
 34. (canceled)
 35. The method of claim1, wherein the preform comprises about 20-60 vol % porosity. 36.(canceled)
 37. (canceled)
 38. (canceled)
 39. A method of forming a bodycomprising: uniaxially hot pressing a preform comprising abrasiveparticles to form a body having a relief extending from a plane whichextends parallel to an axis of pressing.
 40. The method of claim 39,further comprising forming the body such that the final shape of thebody is asymmetric around the axis of pressing, and wherein the planedefines an exterior surface of the body.
 41. (canceled)
 42. The methodof claim 39, wherein uniaxially hot pressing comprises forming a reliefin the body during pressing, wherein the relief extends at an angle tothe axis of pressing.
 43. (canceled)
 44. (canceled)
 45. (canceled) 46.(canceled)
 47. (canceled)
 48. The method of claim 39, further comprisinguniaxially hot pressing at a temperature within a range of about 600° C.(1112° F.) to about 1100° C. (2012° F.).
 49. (canceled)
 50. (canceled)51. (canceled)
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 86. (canceled)87. (canceled)
 88. A method of forming a composite body comprising:uniaxially hot pressing a green body preform to form a composite body,wherein pressing comprises liquid phase sintering and wherein duringpressing the geometry of the preform is substantially altered. 89.(canceled)
 90. The method of claim 88, wherein during pressing anextension is formed protruding from a surface of the composite body. 91.The method of claim 90, wherein the extension extends from a surface ofthe body at an angle to an axis of pressing.
 92. (canceled) 93.(canceled)
 94. (canceled)
 95. The method of claim 88, wherein pressingcomprises uniaxially hot pressing at a temperature within a range ofabout 600° C. (1112° F.) to about 1100° C. (2012° F.).
 96. (canceled)97. The method of claim 88, further comprising pressing in one of anoxidizing atmosphere, a reducing atmosphere, or an inert atmosphere. 98.(canceled)
 99. The method of claim 88, further comprising placing thegreen body preform in a mold prior to pressing.
 100. (canceled) 101.(canceled)
 102. (canceled)
 103. (canceled)
 104. (canceled) 105.(canceled)
 106. The method of claim 99, further comprising providing amold pack within a die wherein the mold pack comprises a plurality ofmolds and a plurality of green body preforms.
 107. The method of claim106, wherein providing a mold pack within a die comprises loading a moldof the plurality of molds with a green body preform of the plurality ofgreen body preforms.
 108. The method of claim 106, further comprisinguniaxially hot pressing the mold pack.
 109. The method of claim 88,further comprising pressing at least two green body preformssimultaneously.
 110. (canceled)